Method of polishing a substrate comprising polysilicon, silicon oxide and silicon nitride

ABSTRACT

A method for chemical mechanical polishing of a substrate is provided, comprising: providing a substrate, wherein the substrate comprises polysilicon, silicon oxide and silicon nitride; providing a chemical mechanical polishing composition, comprising, as initial components: water; an abrasive; an alkyl aryl polyether sulfonate compound, wherein the alkyl aryl polyether sulfonate compound has a hydrophobic portion having an alkyl group bound to an aryl ring and a nonionic acyclic hydrophilic portion having 4 to 100 carbon atoms; and a substance according to formula I 
     
       
         
         
             
             
         
       
     
     wherein each of R 1 , R 2 , R 3 , R 4 , R 5 , R 6  and R 7  is a bridging group having a formula —(CH 2 ) n —, wherein n is an integer selected from 1 to 10; providing a chemical mechanical polishing pad with a polishing surface; moving the polishing surface relative to the substrate; dispensing the chemical mechanical polishing composition onto the polishing surface; and, abrading at least a portion of the substrate to polish the substrate; wherein at least some of the polysilicon is removed from the substrate; and, wherein at least some of the silicon oxide and silicon nitride is removed from the substrate.

The present invention relates to chemical mechanical polishingcompositions and methods of using the same. More particularly, thepresent invention relates to chemical mechanical polishing compositionsfor polishing a substrate having polysilicon in the presence of siliconoxide and silicon nitride.

In the fabrication of integrated circuits and other electronic devices,multiple layers of conducting, semiconducting and dielectric materialsare deposited on or removed from a surface of a semiconductor wafer.Thin layers of conducting, semiconducting, and dielectric materials maybe deposited by a number of deposition techniques. Common depositiontechniques in modern processing include physical vapor deposition (PVD),also known as sputtering, chemical vapor deposition (CVD),plasma-enhanced chemical vapor deposition (PECVD), and electrochemicalplating (ECP).

As layers of materials are sequentially deposited and removed, theuppermost surface of the wafer becomes non-planar. Because subsequentsemiconductor processing (e.g., metallization) requires the wafer tohave a flat surface, the wafer needs to be planarized. Planarization isuseful in removing undesired surface topography and surface defects,such as rough surfaces, agglomerated materials, crystal lattice damage,scratches, and contaminated layers or materials.

Chemical mechanical planarization, or chemical mechanical polishing(CMP), is a common technique used to planarize substrates, such assemiconductor wafers. In conventional CMP, a wafer is mounted on acarrier assembly and positioned in contact with a polishing pad in a CMPapparatus. The carrier assembly provides a controllable pressure to thewafer, pressing it against the polishing pad. The pad is moved (e.g.,rotated) relative to the wafer by an external driving force.Simultaneously therewith, a polishing composition (“slurry”) or otherpolishing solution is provided between the wafer and the polishing pad.Thus, the wafer surface is polished and made planar by the chemical andmechanical action of the pad surface and slurry.

One method used for isolating elements of a semiconductor device,referred to a shallow trench isolation (STI) process, conventionallyinvolved use of a silicon nitride layer formed on a silicon substrate,shallow trenches formed in the silicon nitride layer and a dielectricmaterial (e.g., an oxide) is deposited to fill the trenches. Typicallyan excess of dielectric material is deposited on top of the substrate toensure complete filling of the trenches. The excess dielectric materiallayer is then removed to expose the silicon nitride layer using chemicalmechanical planarization techniques.

Past device designs emphasized chemical mechanical planarizationselectivity for silicon oxide versus silicon nitride (i.e., higherremoval rate for silicon nitride relative to removal rate of siliconnitride). In these device designs, the silicon nitride layer served as astopping layer for the chemical mechanical planarization process.

Certain recent device designs demand polishing compositions that provideselectivity for at least one of silicon oxide and silicon nitride inpreference to polysilicon (i.e., higher removal rate for at least one ofsilicon oxide and silicon nitride relative to the removal rate forpolysilicon) for use in chemical mechanical planarization processes.

One polishing formulation for use in a chemical mechanical planarizationprocess that provides selectivity for at least one of silicon oxide andsilicon nitride relative to polysilicon is disclosed in U.S. PatentApplication Publication No. 2007/0077865 to Dysard, et al. Dysard, etal. discloses a method of chemically mechanically polishing a substrate,which method comprises: (i) contacting a substrate comprisingpolysilicon and a material selected from silicon oxide and siliconnitride with a chemical mechanical polishing system comprising: (a) anabrasive, (b) a liquid carrier, (c) about 1 ppm to about 100 ppm, basedon the weight of the liquid carrier and any components dissolved orsuspended therein, of a polyethylene oxide/polypropylene oxide copolymerhaving an HLB of about 15 or less, and (d) a polishing pad, (ii) movingthe polishing pad relative to the substrate, and (iii) abrading at leasta portion of the substrate to polish the substrate.

Another polishing formulation for use in a chemical mechanicalplanarization process that provides selectivity for at least one ofsilicon oxide and silicon nitride relative to polysilicon is disclosedin U.S. Pat. No. 6,626,968 to Park, et al. Park, et al. disclose achemical mechanical polishing composition in slurry form having a pH of7 to 11 for simultaneously polishing a surface having a silicon oxidelayer and a polysilicon layer, said slurry composition consistingessentially of water, abrasive grains selected from the group consistingof silica (SiO₂), alumina (Al₂O₃), ceria (CeO₂), magania (Mn₂O₃), andmixtures thereof, and about 0.001% to about 5% by weight of a polymeradditive selected from the group consisting of poly vinyl methyl ether(PVME), poly ethylene glycol (PEG), poly oxyethylene 23 lauryl ether(POLE), poly propanoic acid (PPA), poly acrylic acid (PAA), poly etherglycol bis ether (PEGBE), and mixtures thereof wherein the polymeradditive improves the selectivity ratio for removal of silicon oxidelayer relative to removal of the polysilicon layer.

Notwithstanding, to support the dynamic field of device designs for usein the manufacture of semiconductor systems there exists a continuedneed for chemical mechanical polishing compositions formulated toprovide a desirable balance of polishing properties to suit changingdesign needs. For example, there remains a need for chemical mechanicalpolishing compositions that exhibit a tailored removal rate and aremoval rate selectivity that favors the removal of silicon nitride andsilicon oxide relative to polysilicon; and that also favors the removalof silicon oxide relative to silicon nitride.

The present invention provides a method for chemical mechanicalpolishing of a substrate, comprising: providing a substrate, wherein thesubstrate comprises polysilicon, silicon oxide and silicon nitride;providing a chemical mechanical polishing composition, comprising(preferably consisting essentially of), as initial components: water; anabrasive; an alkyl aryl polyether sulfonate compound, wherein the alkylaryl polyether sulfonate compound has a hydrophobic portion having analkyl group bound to an aryl ring and a nonionic acyclic hydrophilicportion having 4 to 100 carbon atoms; and a substance according toformula I

wherein each of R¹, R², R³, R⁴, R⁵, R⁶ and R⁷ is a bridging group havinga formula —(CH₂)_(n)—, wherein n is an integer selected from 1 to 10;providing a chemical mechanical polishing pad with a polishing surface;moving the polishing surface relative to the substrate; dispensing thechemical mechanical polishing composition onto the polishing surface;and, abrading at least a portion of the substrate to polish thesubstrate; wherein at least some of the polysilicon is removed from thesubstrate; and wherein at least some of the silicon oxide and siliconnitride is removed from the substrate.

The present invention also provides a method for chemical mechanicalpolishing of a substrate, comprising: providing a substrate, wherein thesubstrate comprises polysilicon, silicon oxide and silicon nitride;providing a chemical mechanical polishing composition, comprising(preferably consisting essentially of), as initial components: water; anabrasive; an alkyl aryl polyether sulfonate compound, wherein the alkylaryl polyether sulfonate compound has a hydrophobic portion having analkyl group bound to an aryl ring and a nonionic acyclic hydrophilicportion having 4 to 100 carbon atoms; and a substance according toformula I

wherein each of R¹, R², R³, R⁴, R⁵, R⁶ and R⁷ is a bridging group havinga formula —(CH₂)_(n)—, wherein n is an integer selected from 1 to 10;providing a chemical mechanical polishing pad with a polishing surface;moving the polishing surface relative to the substrate; dispensing thechemical mechanical polishing composition onto the polishing surface;and, abrading at least a portion of the substrate to polish thesubstrate; wherein at least some of the polysilicon is removed from thesubstrate; wherein at least some of the silicon oxide and siliconnitride is removed from the substrate; and, wherein the chemicalmechanical polishing composition exhibits a polishing pH of 2 to 5.

The present invention further provides a method for chemical mechanicalpolishing of a substrate, comprising: providing a substrate, wherein thesubstrate comprises polysilicon, silicon oxide and silicon nitride;providing a chemical mechanical polishing composition, comprising(preferably consisting essentially of), as initial components: water; anabrasive; an alkyl aryl polyether sulfonate compound, wherein the alkylaryl polyether sulfonate compound has a formula

wherein R is a branched C₆₋₁₀ alkyl group; x is 2 to 8; and, M isselected from the group consisting of H, Na, K, L₁ and NH₄; anddiethylenetriaminepentakis(methylphosphonic acid); providing a chemicalmechanical polishing pad with a polishing surface; moving the polishingsurface relative to the substrate; dispensing the chemical mechanicalpolishing composition onto the polishing surface; and, abrading at leasta portion of the substrate to polish the substrate; wherein at leastsome of the polysilicon is removed from the substrate; wherein at leastsome of the silicon oxide and silicon nitride is removed from thesubstrate; and, wherein the chemical mechanical polishing compositionexhibits a polishing pH of 2 to 5, adjusted with an inorganic acid.

DETAILED DESCRIPTION

The chemical mechanical polishing method of the present invention isuseful for polishing a substrate comprising polysilicon in combinationwith silicon oxide and silicon nitride. The chemical mechanicalpolishing composition used in the method of the present inventioncontains a polysilicon removal rate suppressing amount of an alkyl arylpolyether sulfonate compound in combination with a substance accordingto formula I. Incorporation of the substance according to formula Ifacilitates tuning of the chemical mechanical polishing composition'sremoval rate selectivity between silicon oxide and silicon nitride,while exhibiting a minimal effect on the polysilicon removal rate.Specifically, incorporation of the substance according to formula I incombination with the alkyl aryl polyether sulfonate compound increasesthe silicon oxide removal rate relative to the silicon nitride removalrate with minimal effect on the removal rate of polysilicon.

The term “substantially lower” used herein and in the appended claimsregarding the removal rate suppression (for removal rate measured inÅ/min) resulting from the addition of an alkyl aryl polyether sulfonatecompound in combination with a substance according to formula Ito thechemical mechanical polishing composition means that the removal rate ofpolysilicon is ≧50% lower. That is, the following expression will besatisfied when the polysilicon removal rate is substantially lower:

((A ₀ −A)/A ₀)*100≧50

wherein A is the polysilicon removal rate in Å/min for a chemicalmechanical polishing composition used in the method of the presentinvention containing an alkyl aryl polyether sulfonate compound incombination with a substance according to formula I; A₀ is thepolysilicon removal rate in Å/min obtained under identical conditionsexcept that the alkyl aryl polyether sulfonate compound and thesubstance according to formula I are absent from the chemical mechanicalpolishing composition.

The term “minimal effect” used herein and in the appended claims inreference to the change in removal rate of polysilicon (for removal ratemeasured in Å/min) resulting from the addition of a substance accordingto formula I to the chemical mechanical polishing composition means thatthe removal rate of polysilicon changes by ≦20%. That is, the followingexpression will be satisfied when the addition of the substanceaccording to formula I to the chemical mechanical polishing compositionhas a minimal effect on the polysilicon removal rate:

(the absolute value of (B ₀ −B)/B ₀)*100≦20

wherein B is the polysilicon removal rate in Å/min for a chemicalmechanical polishing composition used in the method of the presentinvention containing an alkyl aryl polyether sulfonate compound incombination with a substance according to formula I; B₀ is thepolysilicon removal rate in Å/min obtained under identical conditionsexcept that the substance according to formula I is absent from thechemical mechanical polishing composition.

The alkyl aryl polyether sulfonate compound used in the chemicalmechanical polishing composition used in the chemical mechanicalpolishing method of the present invention can be represented by thegeneral formula R—SO₃H or as a salt, R—SO₃ ⁻, wherein R comprises ahydrophobic portion and a nonionic acyclic hydrophilic portion. Thesulfonic acid moiety (i.e., —SO₃H) and the sulfonate moiety (—SO₃ ⁻) areused interchangeably herein.

The hydrophobic portion in the alkyl aryl polyether sulfonate compoundcomprises an alkyl group bound to an aryl ring, In particular, thehydrophobic portion comprises an alkyl group having 4 to 24 carbon atomsbound to an aryl ring, preferably a benzene ring. Preferably, thehydrophobic portion comprises an alkyl group having 4 to 15 carbon atomsbound to a benzene ring. More preferably, the hydrophobic portioncomprises an alkyl group having 6 to 10 carbon atoms bound to a benzenering. The alkyl group bound to the aryl ring can be either a straightchain or branched chain. The alkyl group bound to the aryl ring can besaturated or unsaturated. Most preferably, the alkyl group bound to thearyl ring is a branched chain, saturated alkyl group having 6 to 10carbon atoms.

The nonionic acyclic hydrophilic portion in the alkyl aryl polyethersulfonate compound contains 4 to 100 carbon atoms. Preferably, thenonionic acyclic hydrophilic portion contains 6 to 50 carbon atoms.Still more preferably, the nonionic acyclic hydrophilic portion contains6 to 20 carbon atoms. The nonionic acyclic hydrophilic portion can beeither a straight chain or branched chain. The nonionic acyclichydrophilic portion can be saturated or unsaturated. Preferably, thenonionic acyclic hydrophilic portion is a saturated or unsaturated,straight chain polyalkylene oxide. Most preferably, the nonionic acyclichydrophilic portion is a straight chain of polyethylene oxide.

The alkyl aryl polyether sulfonate compound is optionally added to thechemical mechanical polishing composition used in the method of thepresent invention, as an ammonium, potassium, quaternary ammonium,sodium or lithium salt. Preferably, the alkyl aryl polyether sulfonatecompound is added to the chemical mechanical polishing composition usedin the method of the present invention as a sodium salt.

Preferably, the alkyl aryl polyether sulfonate compound has a formula

wherein R is a branched C₆₋₁₀ alkyl group; x is 2 to 8; and M isselected from the group consisting of H, Na, K, L₁ and NH₄ (morepreferably H and Na; most preferably M is Na).

The amount of alkyl aryl polyether sulfonate compound used in thechemical mechanical polishing composition used in the chemicalmechanical polishing method of the present invention is selected totailor the polysilicon removal rate relative to the removal rate of atleast one of silicon oxide and silicon nitride. The chemical mechanicalpolishing composition used preferably contains, as an initial component,0.0001 to 1 wt % of the alkyl aryl polyether sulfonate compound. Morepreferably, the chemical mechanical polishing composition usedcomprises, as an initial component, 0.01 to 1 wt %, still morepreferably 0.01 to 0.1 wt %, most preferably 0.01 to 0.05 wt %, of thealkyl aryl polyether sulfonate compound.

The chemical mechanical polishing composition used in the chemicalmechanical polishing method of the present invention contains, as aninitial component, a substance according to formula I

wherein each of R¹, R², R⁵, R⁶ and R⁷ is a bridging group having aformula —(CH₂)_(n)—, wherein n is an integer selected from 1 to 10.Preferably, n is an integer independently selected from 1 to 4 for eachof R¹, R², R³, R⁴, R⁵, R⁶ and R⁷. More preferably, n is an integerindependently selected from 2 to 4 for each of R¹, R², R³, R⁴, R⁵, R⁶and R⁷. Most preferably the a substance according to formula I isdiethylenetriaminepentakis(methylphosphonic acid), which has thefollowing formula

Optionally, one or more of the nitrogens in the substance according toformula I can be provided in a quaternary form, wherein the nitrogenassumes a positive charge.

The chemical mechanical polishing composition used in the chemicalmechanical polishing method of the present invention comprises, as aninitial component, 0.001 to 1 wt % of the substance according to formulaI. In some preferred applications, the chemical mechanical polishingcomposition comprises, as an initial component, 0.001 to 0.2 wt %, morepreferably 0.008 to 0.03 wt %, most preferably 0.009 to 0.015 wt % ofthe substance according to formula I.

The water contained in the chemical mechanical polishing compositionused in the chemical mechanical polishing method of the presentinvention is preferably at least one of deionized and distilled to limitincidental impurities.

The chemical mechanical polishing composition used in the chemicalmechanical polishing method of the present invention contains 0.1 to 40wt % abrasive; preferably 5 to 25 wt % abrasive. The abrasive usedpreferably has an average particle size of ≦100 nm; more preferably 10to 100 nm; most preferably 25 to 60 nm.

Abrasive suitable for use in the chemical mechanical polishingcomposition used in the chemical mechanical polishing method of thepresent invention include, for example, inorganic oxides, inorganichydroxides, inorganic hydroxide oxides, metal borides, metal carbides,metal nitrides, polymer particles and mixtures comprising at least oneof the foregoing. Suitable inorganic oxides include, for example, silica(SiO₂), alumina (Al₂O₃), zirconia (ZrO₂), ceria (CeO₂), manganese oxide(MnO₂), titanium oxide (TiO₂) or combinations comprising at least one ofthe foregoing oxides. Modified forms of these inorganic oxides, such as,organic polymer-coated inorganic oxide particles and inorganic coatedparticles can also be utilized if desired. Suitable metal carbides,boride and nitrides include, for example, silicon carbide, siliconnitride, silicon carbonitride (SiCN), boron carbide, tungsten carbide,zirconium carbide, aluminum boride, tantalum carbide, titanium carbide,or combinations comprising at least one of the foregoing metal carbides,boride and nitrides.

The preferred abrasive for use in the chemical mechanical polishingcomposition used in the chemical mechanical polishing method of thepresent invention is colloidal silica. Preferably, the colloidal silicaused contains at least one of fumed silica, precipitated silica andagglomerated silica. Preferably, the colloidal silica used has anaverage particle size of ≦100 nm, more preferably 10 to 100 nm, mostpreferably 25 to 60 nm; and accounts for 0.1 to 40 wt %, preferably 1 to30 wt %; most preferably 15 to 25 wt % of the chemical mechanicalpolishing composition.

The chemical mechanical polishing composition used in the chemicalmechanical polishing method of the present invention optionally furthercomprises additional additives selected from dispersants, surfactants,buffers, anti-foaming agents and biocides.

The chemical mechanical polishing composition used in the chemicalmechanical polishing method of the present invention has a pH of ≦5,preferably 2 to 4, more preferably 2 to 3. The chemical mechanicalpolishing composition used can include inorganic and organic pHadjusting agent. Optionally, the pH adjusting agent is selected from aninorganic acid (e.g., nitric acid, sulfuric acid, hydrochloric acid andphosphoric acid).

The substrate polished in the chemical mechanical polishing method ofthe present invention comprises polysilicon, silicon oxide and siliconnitride.

The polysilicon in the substrate can be any suitable polysiliconmaterial known in the art. The polysilicon can be in any suitable phase,and can be amorphous, crystalline or a combination thereof.

The silicon oxide in the substrate, if present, can be any suitablesilicon oxide material known in the art; for example,borophosphosilicate glass (BPSG), plasma-etched tetraethyl orthosilicate (PETEOS), thermal oxide, undoped silicate glass, high densityplasma (HDP) oxide.

The silicon nitride in the substrate, if present, can be any suitablesilicon nitride material known in the art; for example, Si₃N₄.

The chemical mechanical polishing pad used in the chemical mechanicalpolishing method of the present invention can by any suitable polishingpad known in the art. The chemical mechanical polishing pad mayoptionally be selected from woven and non-woven polishing pads. Thechemical mechanical polishing pad can be made of any suitable polymer ofvarying density, hardness, thickness, compressibility and modulus. Thechemical mechanical polishing pad can be grooved and perforated asdesired.

The alkyl aryl polyether sulfonate compound in combination with thesubstance according to formula I contained in the chemical mechanicalpolishing composition used in the chemical mechanical polishing methodof the present invention preferably suppresses the removal rate ofpolysilicon (as measured in angstroms per minute, Å/min) in a greaterdifferential rate than it suppresses the removal rate of at least one ofsilicon oxide and silicon nitride. If we define the relativemodification (ΔX) of removal rate of a film X as ΔX=(X₀−X)/X₀, whereinX₀ and X stand for the removal rates of film X, measured in Å/min usinga polishing composition without (X₀) and with (X) the addition of analkyl aryl polyether sulfonate compound in combination with a substanceaccording to formula I. Inclusion of an alkyl aryl polyether sulfonatecompound in combination with a substance according to formula I in thechemical mechanical polishing composition used in the method of thepresent invention preferably satisfies at least one of the followingequations (i) Δpolysilicon>ΔSilicon oxide and (ii) Δpolysilicon>ΔSi₃N₄,as measured under the polishing conditions set forth in the Examples.For example, if polishing under the conditions set forth in the Exampleswith an alkyl aryl polyether sulfonate compound and substance accordingto formula I free composition provides a control removal rate X₀=500Å/min for polysilicon and 500 Å/min for silicon dioxide and siliconnitride; and adding an alkyl aryl polyether sulfonate compound incombination with a substance according to formula I to the polishingcomposition reduces the removal rate of polysilicon to X=300 Å/min, thenthe removal rate of at least one of silicon dioxide and silicon nitridemust be >300 Å/min.

Preferably, in the chemical mechanical polishing method of the presentinvention, the polishing removal rate of polysilicon exhibited by thechemical mechanical polishing composition comprising an alkyl arylpolyether sulfonate compound in combination with a substance accordingto formula I is substantially lower than the removal rate of thepolysilicon obtained under the same conditions except for the absence ofthe alkyl aryl polyether sulfonate compound and the substance accordingto formula I. Preferably, polysilicon removal rate suppression obtainedthrough addition of the alkyl aryl polyether sulfonate compound incombination with the substance according to formula I to the chemicalmechanical polishing composition used in the method of the presentinvention is ≧50%; more preferably ≧60%; most preferably ≧80% (i.e.,removal rate suppression=((A₀−A)/A₀)*100)), as measured under thepolishing conditions set forth in the Examples. Typically, thepolysilicon removal rate suppression obtained through the addition ofthe alkyl aryl polyether sulfonate compound in combination with thesubstance according to formula I to the chemical mechanical polishingcomposition used in the method of the present invention is ≦200%.

Preferably, the chemical mechanical polishing composition used in thechemical mechanical polishing method of the present invention exhibits aremoval rate suppression for polysilicon of ≧50%, more preferably ≧60%most preferably ≧80% (i.e., removal rate suppression=((A₀−A)/A₀)*100)),as measured under the polishing conditions set forth in the Examples;and exhibits a removal rate change for at least one of silicon oxide andsilicon nitride<30%; more preferably ≦20%; most preferably ≦10% (i.e.,removal rate change=((absolute value of (C₀−C))/C₀)*100, wherein C isthe silicon oxide or silicon nitride removal rate in Å/min for achemical mechanical polishing composition used in the method of thepresent invention containing an alkyl aryl polyether sulfonate compoundin combination with a substance according to formula I; C₀ is thesilicon oxide or silicon nitride removal rate obtained under identicalconditions except that the alkyl aryl polyether sulfonate compound andthe substance according to formula I are absent from the chemicalmechanical polishing composition), as measured under the polishingconditions set forth in the Examples.

Preferably, in the chemical mechanical polishing method of the presentinvention, the removal rate of silicon oxide relative to that of siliconnitride exhibited by the chemical mechanical polishing compositioncomprising an alkyl aryl polyether sulfonate compound in combinationwith a substance according to formula I is substantially higher than theremoval rate of silicon oxide relative to that of silicon nitrideobtained under the same conditions except for the absence of thesubstance according to formula I. Preferably, the silicon oxide removalrate enhancement relative to silicon nitride obtained through theaddition of the substance according to formula Ito the chemicalmechanical polishing composition used in the method of the presentinvention is ≧50%; more preferably ≧75%; most preferably ≧100% (i.e.,removal rate enhancement ((r₀−r)/r₀)*100)); wherein r₀ is (the removalrate of silicon oxide/the removal rate of silicon nitride) using achemical mechanical polishing composition of the present inventioncontaining an alkyl aryl polyether sulfonate compound in combinationwith a substance according to formula I; and wherein r is (the removalrate of silicon oxide/the removal rate of silicon nitride) obtainedunder identical conditions except that the substance according toformula I is absent from the chemical mechanical polishing composition),as measured under the polishing conditions set forth in the Examples.

Preferably, the chemical mechanical polishing method of the presentinvention can be used to polish a substrate with a silicon nitrideremoval rate of ≧500 Å/min, preferably ≧800 Å/min, more preferably≧1,000 Å/min, most preferably ≧1,200 Å/min, as measured under thepolishing conditions set forth in the Examples; a silicon nitride toamorphous polysilicon removal rate selectivity of ≧5:1, preferably ≧6:1,more preferably ≧7:1 (i.e., removal rate of silicon nitride:removal rateof amorphous polysilicon), as measured under the polishing conditionsset forth in the Examples; and a silicon nitride to crystallinepolysilicon removal rate selectivity of ≧25:1; preferably ≧40:1; morepreferably ≧50:1 (i.e., removal rate of silicon nitride:removal rate ofcrystalline polysilicon), as measured under the polishing conditions setforth in the Examples.

Preferably, the chemical mechanical polishing method of the presentinvention can be used to polish a substrate with a silicon oxide removalrate of ≧500 Å/min, preferably ≧1,000 Å/min, more preferably ≧1,200Å/min, as measured under the polishing conditions set forth in theExamples; a silicon oxide to amorphous polysilicon selectivity of ≧5:1,preferably ≧8:1, more preferably ≧10:1 (i.e., removal rate of siliconoxide:removal rate of amorphous polysilicon), as measured under thepolishing conditions set forth in the Examples; and, a silicon oxide tocrystalline polysilicon removal rate selectivity of ≧25:1; preferably≧50:1; more preferably ≧60:1 (i.e., removal rate of siliconoxide:removal rate of crystalline polysilicon), as measured under thepolishing conditions set forth in the Examples.

Preferably, the chemical mechanical polishing method of the presentinvention can be used to polish a substrate with a silicon nitrideremoval rate of ≧500 Å/min, preferably ≧800 Å/min, more preferably≧1,000 Å/min, most preferably ≧1,200 Å/min; a silicon nitride toamorphous polysilicon removal rate selectivity of ≧5:1, preferably ≧6:1,more preferably ≧7:1 (i.e., removal rate of silicon nitride:removal rateof amorphous polysilicon); a silicon nitride to crystalline polysiliconremoval rate selectivity of ≧25:1; preferably ≧40:1; more preferably≧50:1 (i.e., removal rate of silicon nitride:removal rate of crystallinepolysilicon); a silicon oxide removal rate of ≧500 Å/min, preferably≧1,000 Å/min, more preferably ≧1,200 Å/min; a silicon oxide to amorphouspolysilicon selectivity of ≧5:1, preferably ≧8:1, more preferably ≧10:1(i.e., removal rate of silicon oxide:removal rate of amorphouspolysilicon); and, a silicon oxide to crystalline polysilicon removalrate selectivity of ≧25:1; preferably ≧50:1; more preferably ≧60:1(i.e., removal rate of silicon oxide:removal rate of crystallinepolysilicon), as measured under the polishing conditions set forth inthe Examples.

Preferably, the chemical mechanical polishing method of the presentinvention simultaneously provides selective polishing (i.e., removal) ofboth silicon oxide and silicon nitride relative to polysilicon (i.e.,exhibits a higher removal rate for both silicon oxide and siliconnitride relative to the removal rate for polysilicon, as measured underthe polishing conditions set forth in the Examples). The amount of alkylaryl polyether sulfonate compound and the substance according to formulaI contained in the chemical mechanical polishing composition used in thechemical mechanical polishing method of the present invention can beselected to tailor the polysilicon removal rate relative to the removalrate of at least one of silicon nitride and silicon oxide and to alsotailor the removal rate of silicon oxide to silicon nitride.

The chemical mechanical polishing composition used in the chemicalmechanical polishing method of the present invention enables operationwith a low nominal polishing pad pressure, for example at 3 to 35 kPa.The low nominal polishing pad pressure improves polishing performance byreducing scratching and other undesired polish defects and minimizesdamage to fragile materials.

Some embodiments of the present invention will now be described indetail in the following Examples.

Example 1 Chemical Mechanical Polishing Compositions

The chemical mechanical polishing compositions (CMPC's) tested aredescribed in Table 1. The chemical mechanical polishing composition A isa comparative formulation, which is not within the scope of the claimedinvention.

TABLE 1 Alkyl aryl polyether substance sulfonate of formula compound^(r)

Abrasive^(£) Final CMPC (wt %) (wt %) (wt %) pH^(¥) A — — 12 2.5 1 0.010.1 10 2.5 2 0.02 0.1 10 2.5 3 0.01 — 10 2.5 ^(r)the alkyl arylpolyether sulfonate compound used in the Examples was according to theformula

wherein x is 2; and M is Na (specifically Triton ® X200 available fromThe Dow Chemical Company).

ubstance of formula I used wasdiethylenetriaminepentakis(methylphosphonic acid) ^(£)the abrasive usedin the Examples was Klebosol ® PL1598B25 colloidal silica (manufacturedby AZ Electronic Materials and available from The Dow Chemical Company).^(¥)the composition pH was adjusted as necessary using HNO₃ or KOH.

Example 2 Polishing Tests

Chemical mechanical polishing compositions A, 1 and 2 described in Table1 were tested using 200 mm blanket wafers, specifically (A) TEOSdielectric wafers; (B) Si₃N₄ dielectric wafers and (C) amorphouspolysilicon dielectric wafers and (D) crystalline polysilicon dielectricwafers. An Applied Materials Mirra® CMP polishing platform was used topolish all of the blanket wafers in the Examples using a polishing padcomprising a polyurethane polishing layer containing polymeric hollowcore microparticles and a polyurethane impregnated non-woven subpad(namely an IC1010™ polishing pad commercially available from Rohm andHaas Electronic Materials CMP Inc.). The polishing conditions used inall of the Examples included a platen speed of 93 rpm; a carrier speedof 87 rpm; with a polishing medium flow rate of 200 ml/min and adownforce of 20.7 kPa. Removal rates for each of the polish experimentsare provided in Table 2. Note that the removal rates were calculatedfrom the before and after polish film thickness. Specifically, theremoval rates were determined using a SpectraFX 200 optical thin-filmmetrology system available from KLA-Tencor.

TABLE 2 TEOS Amorphous Crystalline removal rate Si₃N₄ polysiliconpolysilicon CMPC (Å/min) (Å/min) (Å/min) (Å/min) A 1296 1412 649 223 11452 1013 213 55 2 1228 975 122 19

Example 2 Polishing Tests

Chemical mechanical polishing composition 3 described in Table 1 weretested using 200 mm blanket wafers, specifically (A) TEOS dielectricwafers; (B) Si₃N₄ dielectric wafers and (C) amorphous polysilicondielectric wafers. A Strasbaugh nSpire™ CMP system model 6EC rotary typepolishing platform was used to polish all of the blanket wafers in theExamples using a polishing pad comprising a polyurethane polishing layercontaining polymeric hollow core microparticles and a polyurethaneimpregnated non-woven subpad (namely an IC1010™ polishing padcommercially available from Rohm and Haas Electronic Materials CMPInc.). The polishing conditions used in all of the Examples included aplaten speed of 93 rpm, a carrier speed of 87 rpm; with a polishingmedium flow rate of 200 ml/min and a downforce of 20.7 kPa. Removalrates for each of the polish experiments are provided in Table 3. Notethat the removal rates were calculated from the before and after polishfilm thickness. Specifically, the removal rates were determined using aSpectraFX 200 optical thin-film metrology system available fromKLA-Tencor.

TABLE 3 TEOS removal rate Si₃N₄ Amorphous polysilicon CMPC (Å/min)(Å/min) (Å/min) 3 812 1588 248

1. A method for chemical mechanical polishing of a substrate,comprising: providing a substrate, wherein the substrate comprisespolysilicon, silicon oxide and silicon nitride; providing a chemicalmechanical polishing composition, comprising, as initial components:water; an abrasive; an alkyl aryl polyether sulfonate compound, whereinthe alkyl aryl polyether sulfonate compound has a hydrophobic portionhaving an alkyl group bound to an aryl ring and a nonionic acyclichydrophilic portion having 4 to 100 carbon atoms; and a substanceaccording to formula I

wherein each of R¹, R², R³, R⁴, R⁵, R⁶ and R⁷ is a bridging group havinga formula —(CH₂)_(n)—, wherein n is an integer selected from 1 to 10;providing a chemical mechanical polishing pad with a polishing surface;moving the polishing surface relative to the substrate; dispensing thechemical mechanical polishing composition onto the polishing surface;and, abrading at least a portion of the substrate to polish thesubstrate; wherein at least some of the polysilicon is removed from thesubstrate; and, wherein at least some of the silicon oxide and siliconnitride is removed from the substrate.
 2. The method of claim 1, whereinthe chemical mechanical polishing composition exhibits a silicon oxideto polysilicon removal rate selectivity of ≧5:1.
 3. The method of claim2, wherein the chemical mechanical polishing composition exhibits asilicon oxide removal rate of ≧500 Å/min; with a platen speed of 93revolutions per minute, a carrier speed of 87 revolutions per minute, achemical mechanical polishing composition flow rate of 200 ml/min, anominal down force of 3 psi on a 200 mm polishing machine; wherein thechemical mechanical polishing pad comprises a polyurethane polishinglayer containing polymeric hollow core microparticles and a polyurethaneimpregnated non-woven subpad.
 4. The method of claim 3, wherein thepolysilicon is amorphous polysilicon, and wherein the chemicalmechanical polishing composition exhibits a silicon oxide to amorphouspolysilicon removal rate selectivity of ≧5:1.
 5. The method of claim 3,wherein the polysilicon is crystalline polysilicon and wherein thechemical mechanical polishing composition exhibits a silicon oxide tocrystalline polysilicon removal rate selectivity of ≧10:1.
 6. The methodof claim 1, wherein the chemical mechanical polishing compositionexhibits a silicon nitride to polysilicon removal rate selectivity of≧5:1.
 7. The method of claim 6, wherein the chemical mechanicalpolishing composition exhibits a silicon nitride removal rate of ≧500Å/min; with a platen speed of 93 revolutions per minute, a carrier speedof 87 revolutions per minute, a chemical mechanical polishingcomposition flow rate of 200 ml/min, a nominal down force of 3 psi on a200 mm polishing machine; wherein the chemical mechanical polishing padcomprises a polyurethane polishing layer containing polymeric hollowcore microparticles and a polyurethane impregnated non-woven subpad. 8.The method of claim 7, wherein the polysilicon is amorphous polysiliconeand wherein the chemical mechanical polishing composition exhibits asilicon nitride to amorphous polysilicon removal rate selectivity of≧5:1.
 9. The method of claim 7, wherein the polysilicon is crystallinepolysilicon and wherein the chemical mechanical polishing compositionexhibits a silicon nitride to crystalline polysilicon removal rateselectivity of ≧10:1.
 10. The method of claim 1, wherein the alkyl arylpolyether sulfonate compound has a formula

wherein R is a branched C₆₋₁₀ alkyl group; x is 2 to 8; and, M isselected from the group consisting of H, Na, K, Li and NH₄; and whereinthe substance according to formula I isdiethylenetriaminepentakis(methyl phosphonic acid).